New alkoxyphenyl azomethine phenyl toluate liquid crystals

A series of alkoxyphenyl azomethine phenyl toluates was synthesised and investigated for thermal and liquid crystalline behaviour. All the synthesised compounds were characterised using FT-IR, 1H NMR and 13C NMR spectroscopy. The materials demonstrated high thermal stability in thermogravimetric analysis (TGA), undergoing decomposition above 280°C. Mesomorphic properties were investigated using a combination of differential scanning calorimetry (DSC) and polarising optical microscopy (POM). All final compounds exhibited liquid-crystalline properties, displaying textures characteristic of calamitic liquid crystals. There was a tendency for lower homologs to display enantiotropic behaviour (N), while higher homologs exhibited dimesomorphic behaviour (N and SmC). The mesophases were confirmed through X-ray diffraction studies. A comparison with similar compounds revealed that interchanging the positions of methyl and alkoxy end groups influenced the nematic phase stabilities in lower homologues and led to a transition from SmA to SmC in higher homologues.